President Recep Tayyip Erdogan seemed to suggest Turkey would release a detained US pastor in exchange for the extradition of Fetullah Gulen, the US-based alleged mastermind of the failed July 2016 coup.

President Recep Tayyip Erdogan appeared to suggest on Thursday that Turkey could free a detained US pastor if the United States handed over a Muslim cleric living in Pennsylvania, whom Ankara has blamed for a failed military coup last year.

The cleric is Fetullah Gulen. The paster is Andrew Brunson.

Speaking in Ankara, Erdogan said: "'Give us the pastor back', they say. You have one pastor [Gulen] as well. Give him to us," Erdogan said. "Then we will try him [Brunson] and give him to you."

"The [pastor] we have is on trial. Yours is not - he is living in Pennsylvania. You can give him easily. You can give him right away."

Turkey has been unsuccessfully seeking the extradition of Fetullah Gulen, whom Ankara accuses of trying to overthrow the government and presidency in July 2016.

Gulen has denied any role in the coup attempt, in which 250 people were killed, and another 2,000 wounded.

Thousands of people suspected of involvement in the failed coup, or links to Gulen's FETO network, have been detained since the attempted putsch on the night or July 15 last year.

Those detained include Christian missionary Andrew Brunson, who ran a church in Izmir on Turkey's western coast and has been held since October 2016.

Brunson was arrested for allegedly spying, divulging state secrets and for links to the Fetullah Terrorist Organisation (FETO).

Fetullah Gulen speaks to members of the media at his compound, in Saylorsburg, Pennsylvania, in July 2016. (AP)
()

Turkey opens door to exchange

A decree issued in August gave Erdogan authority to approve the exchange of foreigners detained or convicted in Turkey with people held in other countries "in situations required by national security or national interests."

Asked about Erdogan's suggestion of a swap of Gulen for Brunson, US State Department spokeswoman Heather Nauert said, "I can’t imagine that we would go down that road."

Washington maintains that Brunson has been wrongfully imprisoned. Nauert said US diplomats were able to visit him on September 18, and added the State Department would continue to work on his release.

Washington has said the Turkish government has yet to provide enough evidence for the US Justice Department to act on the request for Gulen's extradition.